Hi fair monks!

As I was troubleshooting some old code of mine, I came to a piece of code that was somewhat similar to this test script: 
use strict;

# clean a directory path of extraneous '/'
sub clean_path {
    for (my $i = 0; $i <= $#_; $i++) {
    # match two or more '/' between a pair of
    # other non '/' chars and replace the
    # multiple occurance of '/' with a single '/'.
        $_[$i] =~ s|([^/])[/]{2,}([^/])|$1/$2|g;
    # remove trailing garbage such as '/'...
        $_[$i] =~ s|[/\n\t\s]+$||;
    # also remove silly '/./...' things
        $_[$i] =~ s|\./||g;
        $_[$i] =~ s|/\.$||g; # some path have that wicked '/foo/bar/.'
+ '.' in the end!
    }
}


### MAIN

my $path_list = undef;

## a bunch of code here
## . . . . .
##

## I'm checking that if no path list was provided,
## I use at a 'blank' path so that the loop would 
## execute at least once (as if for root directory).
##
foreach my $some_path ( (defined $path_list && $#$path_list >= 0) ? @{
+$path_list} : "" ) {
    clean_path($some_path);
    # do stuff with path
    print "Working with $some_path\n";
}

print "done\n";

[download]
The error I get when trying to run the script is this: 
  Modification of a read-only value attempted at test.pl line 10, <IN>
+ chunk 1.
        main::clean_path('') called at test.pl line 33

[download]
I can't quite understand what causes this error. I'm sure it's something simple. I'm also wondering whether it's possible to test any variable for being a 'read-only' one?

Thanks for help ;-).

"There is no system but GNU, and Linux is one of its kernels." -- Confession of Faith

In reply to How could I check if a variable is 'read-only'? by vladb

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